Most of the surfaces have roughness down to atomic scales. When two surfaces come into contact, the nature of the roughness determines the properties like friction and wear. Analysis of the rough surface contacts is always complicated by the interaction between the material size effects and the micro-geometry. Contact mechanics could be simplified by decoupling these two effects by magnifying the scale of roughness profile. Also, tailoring the roughness at different scale could show a way to control the friction and wear through surface micro-structure modifications. In this work, the mechanics of contact between a rigid, hard sphere and a surface with a well defined roughness profile is studied through experiments and finite element simulation. The well defined roughness profile is made up of a regular array of pyramidal asperities. This choice of this geometry was mainly dictated by the fabrication processes. The specimens were made out of an aluminium alloy (6351-T6) such that there could be a direct application of the results in controlling the tribological properties during aluminium forming. Experiments on the pyramidal aluminium surface is carried out in a 250 kN Universal Testing Machine (INSTRON 8502 system) using a depth sensing indentation setup. A strain gauge based load cell is used to measure the force of the indentation and a LVDT (Linear Variable Differential Transformer) is used to measure the penetration depth. The load and the displacement were continuously recorded using a data acquisition system. A 3-D finite element framework for studying the elastic-plastic contact of the rough surfaces has been developed with the commercial package (ABAQUS). Systematic studies of indentation were carried out in order to validate the simulations with the experimental observations. The simulation of indentation of flat surface is carried out using the implicit/standard (Backward Euler) procedure, whereas, the explicit finite element method (Forward Euler) is used for simulating rough surface indentation. It is found that the load versus displacement curves obtained from experiments match well with the finite element results (except for the error involved in determining the initial contact point). At indentation depths higher than a value that is determined mainly by the asperity height, the load-displacement characteristics are similar to that pertaining to indentation of a flat, smooth surface. From the finite element results, it is found that at this point, the elastic-plastic boundary is more or less hemispherical as in the case of smooth surface indentation. For certain geometries, it is found that there could exist an elastic island in the sub-surface surrounded by plastically deformed material. This could have interesting applications.

Recently, powders of the size d (0.1 μm < d < 10 μm) have been referred to ultrafine particles. The particle shape considered is assumed to be a sphere of the diameter d. The handling of powders is of great importance for processing of pharmaceuticals, cement, chemicals and other products. Most of these technological processes involve powder compaction, storage, transportation, mixing, etc, therefore, understanding of the fundamentals of particles interaction behaviour is very essential in the design of machines and equipment as well as in powder technology, cleaning of environment and other areas. The dynamic behaviour of particulate systems is very complicated due to the complex interactions between individual particles and their interaction with the surroundings. Understanding the underlying mechanisms can be effectively achieved via particle scale research. The problem of a normal contact may be resolved in a number of ways. In spite of huge progress in experimental techniques, direct lab tests with individual particles are still rather time-consuming and expensive. The interaction of particles as solid bodies is actually a classical problem of contact mechanics. In the case of ultrafine particles, the reduction of the particle size shifts the contact zones into the nanoscale or subnanoscale. Thus, steadily increasing contribution of adhesion has to be considered in the development of the physically correct constitutive models and numerical tools. Consequently, it may... [to full text] / Ultrasmulkios dalelės yra šiuolaikinės chemijos, farmacijos, maisto ir kitų pramonės šakų produktų sudėtinė dalis. Tiriant pramoninius technologinius procesus, neišvengiamai reikalingos teorinės žinios apie ultrasmulkių dalelių elgseną. Išsamus supratimas įmanomas tik atlikus įvairius tyrimus. Pastaruoju metu milteliai, klasifikuojami kaip ultrasmulkios (0,1 < d < 10 μm) dalelės, imti plačiai naudoti pramoniniuose procesuose, todėl suprasti ultrasmulkių dalelių elgsenos fundamentalumą miltelių technologijoje yra labai svarbu. Ultrasmulki dalelė yra itin maža, todėl su ja atlikti fizinį eksperimentą, kuris reikalauja specialios įrangos bei žinių, labai sunku. Tokiu atveju dažniausiai naudojamas skaitinis eksperimentas, kurį galima atlikti virtualiai. Skaitinio eksperimento metu yra tiriamos dinaminės ultrasmulkios dalelės savybės bei sprendžiamas dinaminis uždavinys. Taikant skaitinius modelius bei dalelės judėjimą aprašančias jėgų lygtis, naudojami sąveikos modeliai, apimantys adhezinę, klampią, tamprią bei tampriai plastinę sąveikas. Mikroskopinis adhezinės sąveikos modeliavimas – aktualus mechanikos mokslo uždavinys. Taikant sąveikos modelius, svarbu pritaikyti ir diskrečiųjų elementų metodą, kadangi, norint aprašyti dalelių elgseną, visų pirma reikia su-vokti ir aprašyti dalelės modelį. Dalelės elgsenos skaitiniam modeliavimui siūlomi teoriniai modeliai leidžia tirti dalelės sąveiką su dalele ar tampria puserdve bei sąveikos dinamiką. Šie modeliai galėtų būti pritaikyti... [toliau žr. visą tekstą]

A caracterização de materiais utilizando a técnica de indentação instrumentada difundiu-se significativamente na última década, devido às melhorias dos instrumentos que permitem ensaios por esta técnica e à necessidade de se fazer ensaios em pequenos volumes de materiais, como, por exemplo, em filmes finos e materiais com superfícies modificadas por tratamentos superficiais. Neste texto, abordou-se a elaboração de um algoritmo que permita o estudo da resposta de indentação de superfícies de diferentes materiais metálicos, durante e após o contato com um indentador agudo, empregando simulações por elementos finitos e análise dimensional. Na obtenção do algoritmo analisaram-se os efeitos da formação de borda (pile-up) ou da retração (sink-in) do material indentado, o coeficiente de atrito indentador-amostra, as deformações elásticas do indentador, a geometria do indentador e a variação experimental. As relações obtidas permitiram identificar uma falta fundamental de relação única entre as propriedades mecânicas e a forma da curva de indentação para curvas com razão d r/dmax>0,9, onde d r é a profundidade residual da indentação e dmax é o deslocamento máximo do indentador durante o ensaio. Da mesma forma, concluiu-se que a relação de Sneddon tem que ser corrigida tanto pela geometria da área de contato indentador-amostra quanto pela razão entre os módulos elásticos do material e do indentador (E/Ei). Como a área de contato indentador-amostra é afetada não só pela geometria do indentador mas também pelo nível de pile-up ou sink-in nos indentadores piramidais, uma relação foi identificada entre o nível de pile-up/sink-in e o fator de correção b da equação de Sneddon para os indentadores Vickers e Berkovich. Adicionalmente, pequenas diferenças foram observadas entre as curvas P-h (onde h é a profundidade de indentação abaixo da superfície original da amostra) e as curvas P-d (onde d é o valor da aproximação mútua entre indentador e amostra durante a indentação) para um mesmo valor de módulo reduzido Er quando a razão E/Ei é grande. Assim, o módulo reduzido pode sobreestimar ou subestimar a rigidez do indentador, dependendo das propriedades do material indentado. As análises neste trabalho permitiram igualmente observar que as principais limitações na obtenção das propriedades elasto-plásticas usando a curva de indentação instrumentada vêm da falta de unicidade, seguida pela geometria do indentador, isto é, diferenças entre o cone equivalente e os piramidais Vickers e Berkovich, assim como desvios em relação à geometria ideal do indentador, o que inclui arredondamento da sua ponta. Quando não há unicidade, sabendo-se informações adicionais à curva P-d, por exemplo, o valor da área residual da indentação ou o módulo elástico, uma solução única das propriedades mecânicas pode ser obtida. Em paralelo, a variação experimental pode limitar de forma significativa a precisão no cálculo das propriedades, enquanto o atrito indentador-amostra e as deformações do indentador têm efeitos menos significativos. Em termos gerais, observa-se que as funções que compõem o algoritmo desenvolvido neste trabalho permitem: (i) predizer as curvas carga-deslocamento (curvas P-d), produto do ensaio de indentação instrumentada, para um conjunto de propriedades elasto-plásticas conhecidas; (ii) identificar quando uma mesma curva P-d pode ser obtida de mais de um conjunto de propriedades do material indentado (iii) calcular as propriedades mecânicas (dureza, módulo elástico, coeficiente de encruamento e limite de escoamento) de um material usando a curva P-d quando d r/dmax<0,8 ou faixas de propriedades de materiais quando d r/dmax>0,8 e (iv) calcular as propriedades mecânicas (dureza, módulo elástico, coeficiente de encruamento e limite de escoamento) de um material usando a curva P-d e a área residual da indentação. / The interest in material characterization using instrumented indentation techniques has significantly increased in the last decade, due to improvements in testing instruments and the need to carry out tests on small volumes of materials, such as thin films or materials with surfaces modified by other surface treatments. This work addresses the development of an algorithm to analyze the indentation response of a group of metallic materials, during and after the contact with a sharp indenter, using finite element simulations and dimensional analysis. The formulation of the algorithm considered the effects of pile-up or sink-in of the indented material around the indentation, the friction coefficient between the indenter and the sample, the elastic deformation of the indenter, and the defects of the indenter tip. An analysis considering algorithm output and experimental variation was also conducted. The results allowed identifying a fundamental lack of unique relationship between the mechanical properties and the shape of the indentation curve for indentation curves with ratio d r/dmax>0,9, where d r is the residual indentation depth and dmax is the maximum indenter displacement in the test. Similarly, results allowed concluding that Sneddons equation requires a correction by both the geometry of the contact area and the ratio between the elastic moduli of the material and the indenter (E/Ei). As the shape of contact area is affected not only by the geometry of the indenter but also by the level of pile-up or sink-in in pyramidal indenters, a relationship was observed between the level of pile-up/sink-in and the correction factor b in the Sneddons equation for Vickers and Berkovich indenters. Additionally, it was found that the deformation of the indenter is not fully incorporated into indentation data analysis by the consideration of a reduced modulus (Er). Small differences between P-h curves (where h is the indentation depth below the original surface) and P-d curves (where d is the indenter/sample mutual approach) were observed for the same Er when the ratio E/Ei is large. Thus, the reduced modulus can overestimate or underestimate the indenter stiffness, depending on the mechanical properties of the indented material. Additionally, the analysis in this work has identified that the most important limitations in mechanical properties estimation using the indentation curve arise from the lack of uniqueness, followed by deviations in indenter geometry, such as differences between equivalent cone and pyramidal Vickers or Berkovich and tip defects. When non-uniqueness is present, unique solution may be obtained with the knowledge of additional information, in conjunction with P-d data, such as the residual indentation area or the elastic modulus. Furthermore, even when a unique solution is available the experimental variation may significantly decrease the accuracy in mechanical properties estimation, whereas friction and indenter deformation have less significant effects. In general, it was observed that the proposed algorithm allows: (i) predicting the load-displacement curves P-d of instrumented indentation tests for a set of known elastic-plastic mechanical properties, (ii) identifying when the same P-d curve can be obtained from more than one set of mechanical properties of the indented material, (iii) calculating the mechanical properties (hardness, elastic modulus, yield stress and strain hardening coefficient) from P-d curves when d r/dmax<0,8 or possible ranges for each mechanical property when d r/dmax>0,8 and (iv) calculating the mechanical properties (hardness, elastic modulus, yield stress and strain hardening coefficient) from P-d curves and the knowledge of the residual indentation area.

Polyethylene is a widely-used material in package industries. The fracture behavior of this material has not been studied in the plastic region in many years. In this thesis work, the J-Integral which is one material property used to represent the plastic material strength is calculated through the numerical analysis. To build a correct numerical model, the material behavior is summarized from previous uniaxial tensile test. The result from the fracture experiment for variable initial crack length is used to validate the reliability of the numerical model. The numerical analysis is done by the software ABAQUS which has the function to get the value of J-Integral directly. The final result contains the comparison between experiments and numerical analysis and the value of J-Integral at the crack initiation.

The aim of the thesis is to create an analytical model of frame construction. Determining load at which individual plastic hinges are formed until the collapse of the structure. The analysis is going to be performed by RFEM with an additional module RFDYNAM. Subsequently, the parameters of dynamic relaxation is going to be optimized to specify and speed up the calculations. Finally, the optimized parameters is going to be used to analyze the storeyed frame construction formed Ing. Jan Vales including a comparison of findings.

Ces travaux de thèse portent sur la question de l'assemblage multi-matériaux polymère-acier. Dans un environnement automobile grande série, le rivetage auto-poinçonneur est le procédé d'assemblage proposé qui permet de répondre à la problématique industrielle. Dans un premier temps, la faisabilité de la technique i été étudiée en recherchant l'influence de la vitesse de rivetage et de l'effort serre-flan sur les caractéristiques géométriques du joint riveté et sur la tenue mécanique. Ainsi, il se révèle que l'augmentation de la vitesse de rivetage a un effet favorable: l'effort à la rupture en traction pure augmente de +10% en accord avec l'augmentation de l'ancrage mécanique. Par contre, l'augmentation de l'effort serre-flan a un effet défavorable : l'effort à la rupture en traction pure et en traction-cisaillement diminue de -6.6%. Par la suite, un modèle numérique 2D axisymétrique a été mis au point dans le but de simuler l'opération de rivetage. Les propriétés mécaniques effectives du matériau composite sont estimées par une méthode d'homogénéisation tandis que le comportement mécanique du matériau acier par un modèle élasto-plastique endommageable. Comparée à la coupe transversale issue d'un essai expérimental, la simulation effectuée sous Abaqus 6.10- 1® démontre être capable de correctement prédire la déformée en particulier pour la valeur d'ancrage mécanique. Enfin, un modèle numérique 30 a été développé et permet de simuler des chargements destructifs et asymétriques. L'effort à rupture et les déformées macroscopiques estimées sont en bon accord avec les résultats expérimentaux, grâce notamment à la prise en compte de l'endommagement local de la couche composite. / This thesis work is dealing with the issue of multi-material polymer-steel joining. Within a large-scale automotive environment, self-piercing riveting is the proposed joining technique to tackle the industrial challenge. Firstly, the feasibility of the technique is studied by investigating the influence of the riveting velocity and the sheet holder load on the geometrical characteristics of the riveted joint and the mechanical strength. Thus, it turns out that the increase in riveting velocity has a favorable effect: the joint strength in pure tension mode increases by +10% in agreement with the increase in mechanical anchoring. However, the increase of the sheet holder load has an unfavorable effect: the joint strength in cross tension and in shear modes decreases by -6.6%. Subsequently, an axisymmetrical 20 numerical model has been created enabling the simulation of the riveting operation. The effective mechanical properties of the composite material are estimated by a homogenization method while the mechanical behavior of the steel material is managed through an elastic-plastic model with damage. Compared with a cross section resulting from an experimental test, the simulation carried out under Abaqus 6.10-1® demonstrates being able to correctly predict the deformations, the anchoring value more particularly. Finally, a 30 numerical model has been developed and allows the simulation of destructive and asymmetrical loadings. The joint strength and the macroscopic deformations estimated are in good agreement with the experimental results, especially when taking into account the local damage of the composite laver.

Zunehmendes Downsizing und der Trend zum Leichtbau bei Welle-Nabe-Verbindungen erfordern eine exakte Beschreibung des Systemverhaltens. Elastische Simulationen erfordern im Post-processing die Analyse komplexer Zusammenhänge, welche oftmals nur empirisch begründet sind. Elastisch-Plastische Materialmodelle geben die Möglichkeit Stütz- und Setzeffekte von Passfederverbindungen bereits während der Simulation abzubilden. Die vorliegende Arbeit wendet elastisch-plastische Materialmodelle auf Passfederverbindungen an, um auftretende Versagensmechanismen zu beschreiben. / Downsizing and the trend to lightweight design ofshaft-hub-connections need an accurate description of the behaviour of the system. In post-processing, elastic simulations require a complex analysis based on empiric formula. Using elastic-plastic material models enable the possibility to respect support and set effects of feather key connections within the simulation. The current paper applies elastic-plastic material models to feather key connections in order to describe occurring failure mechanisms.

any experiments demonstrate that isotropic ductile materials used in engineering applications develop anisotropic damage and shows significant variation in elongation to failure. This anisotropic damage is manifest by material microstructural heterogeneities and morphological changes during deformation. The variation in elongation to the failure could be attributed to the uncertainties in the material microstructure and loading conditions. To study this deformation induced anisotropy arising from the initial material heterogeneities, we first performed uncertainty analysis using current form on an internal state variable plasticity and isotropic damage model (Bammann, 1984; Horstemeyer, 2001) to quantify the effect due to variations in material microstructure and loading conditions on elongation to failure. We extend the current isotropic damage form of theory into an anisotropic damage form for ductile material in which material heterogeneities are introduced based on damage distribution functions converted into a damage tensor of second rank. The outcome of this research is a physically motivated, uncertainty-based, anisotropic damage constitutive model that links microstructural features to mechanical properties. This was accomplished by pursuing three sub goals: (1) develop and quantify uncertainty related to material heterogeneities, (2) develop a methodology related to a higher order tensorial rank of damage for void nucleation and void growth, and (3) integrate thermodynamically constrained damage with a rate dependent plasticity constitutive material model. Later, we also proposed a new ISV theory that physically and strongly couples deformation due to damage-related internal defects to metal plasticity.

Neste trabalho são comparados os resultados analíticos de previsão de falha de um vaso nuclear PWR destinado à propulsão naval, contendo oito diferentes tipos de trinca, obtidos segundo a Mecânica da Fratura Elástica-Linear (MFEL) e a correspondente Elasto-Plástica (MFEP). Os resultados são fornecidos em termos da pressão interna e do gradiente de deformações ao longo da espessura da parede do componente estrutural, sendo diretamente aplicáveis às condições impostas e desenvolvidas em ensaios isotérmicos de hidro-pressurização. O elevado nível de conservativismo dos resultados derivados segundo a MFEL, via critério KIC de disparo de clivagem, quando comparados àqueles obtidos por meio da MFEP, através do critério de iniciação de rasgamento dúctil, Ji, e em especial dos critérios J50 e Jinstab.dúctil de falha com base na Teoria da Instabilidade do Rasgamento Dúctil ou Elasto-Plástico (TIRD/TIREP) por intermédio de diagramas J x T (integral-J versus módulo de rasgamento), foi avaliado e quantificado. O intenso efeito das dimensões dos corpos de prova nos resultados obtidos a partir de ambas abordagens, assim como o papel determinante dos entalhes laterais nos ensaios da MFEP foram definitivamente comprovados. Foi também demonstrado o saudável conservativismo das previsões segundo o critério J50 para projeto e serviço seguros de plantas nucleares frente às condições reais em que se verifica analiticamente a instabilidade dúctil do componente trincado, tais como definidas por Jinstab.dúctil, assim como das previsões decorrentes dos processos de extrapolação linear de curvas J-R no espaço J x T quando comparadas às resultantes de extrapolações não-lineares mais frequentemente utilizadas. Com relação aos efeitos exercidos nos resultados de previsão de falha pelo tipo, profundidade e comprimento da trinca contida na parede do vaso de pressão, ficou demonstrado que as trincas de superfície são muito mais críticas que as sub-superficiais de idênticas profundidade e comprimento, assim como que as avaliações de integridade são muito mais sensíveis a mudanças na profundidade da trinca relativamente a alterações no seu comprimento. As aproximações entre os resultados obtidos via J50 e através de Jinstab.dúttil, e entre os resultados obtidos pelos procedimentos de extrapolação linear e não-linear de curvas JMAT-TMAT, são muito mais nítidas para as trincas de superfície menos profundas e, em especial para as embutidas, mesmo aquelas mais críticas. Deste modo, a metodologia aqui aprimorada, destinada em última instância a avaliações de integridade estrutural de vasos PWR em transientes de potência durante a sua vida em serviço, se mostrou absolutamente efetiva no caso das trincas mais prováveis em tais circunstâncias, quais sejam, as de pequenas dimensões e situadas superficialmente na parede do vaso. Ainda, foi verificada a tendência da ocorrência do vazamento do meio pressurizante anteriormente à falha do vaso por instabilidade dúctil nos casos da presença das trincas mais profundas, independentemente de serem elas de superfície ou sub-superficiais e, novamente, de seu comprimento, contribuindo assim para a percepção visual da iminência da falha bem como para eventos de freamento de trinca dúctil, impedindo a falha catastrófica do vaso PWR. Por outro lado, trincas rasas ou meno·s profundas tendem a entrar no regime de instabilidade dúctil muito precocemente, com a essência da propagação se dando de modo instável, causando fratura rápida ou súbita do vaso sem sinal anterior. Finalmente, foi comprovada nesse estudo a aplicabilidade da técnica analítica de normalização linear para o levantamento de curvas J-R, e como consequência JMAT-TMAT, para a avaliação de integridade estrutural de componentes robustos falhando de modo dúctil após considerável, e mensurável, crescimento estável de trinca; também, foi aqui proposto o ajuste logarítmico de dados de curvas J-R, em oposição ao hoje consensualmente utilizado via lei de potência, de modo a computar os efeitos do fenômeno de saturação de J, permitindo assim extrapolações conservativas e seguras para as condições em que se verifica a falha do componente nuclear. / In this work the analytical results related to a nuclear pressure vessel failure conditions as obtained by Linear Elastic Fracture Mechanics (LEFM) and the Elastic-Plastic Fracture Mechanics (EPFM) were compared for eigth different crack types. The results are supplied in terms of internal pressure and strain gradient through the wall thickness of the structural component, and might be directly applied to isothermal hydrotests experiments. The high conservatism of LEFM approach, by using KIC criterion of cleavage triggering, as compared to results obtained via Ji of ductile crack initiation from EPFM approach, and specially to the J50 and Jduct.instab. criteria based on ductile Tearing Instability Theory through J x T (J-integral x tearing modulus) diagrams, was evaluated and quantified. The overriding effect of specimens size over LEFM and EPFM results were definitely proved, as well as the very strong influence of side-grooving the EPFM specimens. It was demonstrated the healthy conservatism of the predictions following the J50 criterion for safe design and service in the nuclear industry facing the real conditions where ductile instability takes place as analytically defined by Jduct.instab.. In the same way the conservatism of the predictions from the linear extrapolation procedure of J-R curves on J x T space, as compared with the most common non-linear process was proved as well. With respect to the effect exerted by type, depth and length of the crack over the results it was demonstrated that surface cracks are more critical than the embedded ones with identical dimensions, being the analytical evaluation much more sensitive to changes in the crack depth than in its length. The approximations among the results obtained from J50 and Jduct.instab. criteria as well as among the results from the linear and non-linear extrapolation procedure are best verified for the less depth surface cracks and specially for the embedded cracks even the largest ones. So, the methodology here improved, aimed in last instance to structural integrity assessment of PWR vessels on power transients during their service life has been shown to be a powerful tool in evaluating the most expected cracks under such circunstances, that is, those having small dimensions and located on surface wall. Still, it was demonstrated the trend for leak-before-ductile instability in the presence of the deepest surface and internal cracks, allowing the visual perception of the threshold of the vessel failure and the development of crack arrest events avoiding catastrofic rupture of the component. Otherwise, shallow cracks are prone to get very fast in the unstable regime of growth, with the essence of the propagation occuring under this condition, conducting to suddenly fracture of the vessel without any prior evidence. Finally, it was proved in this study the accuracy of the linear normalization technique in deriving J-R curves for the assessment of structural integrity of massive components which fail in a ductile way after undergo large stable crack extensions; it was suggested here the logarithmic fit of J-R data points taking in account more properly the J-saturation phenomena and leading to more safe and conservative extrapolation results when compared to resulting from power-law fit.

Caracterizar propriedades de resistência à propagação de trinca em materiais dúcteis é um elemento central em métodos de avaliação de integridade estrutural de dutos destinados ao transporte de gás, petróleo e seus derivados que utilizam os aços ARBL. Sendo assim, o objetivo deste trabalho foi estudar as propriedades de fratura dúctil do aço API 5L X80, através da obtenção da curva de resistência à propagação estável de defeitos (curvas J-R) do material. O ensaio de tenacidade à fratura para obtenção da curva J-R foi conduzido utilizando a técnica do corpo-de-prova único (single specimen) empregando o método da flexibilidade no descarregamento (unloading compliance), segundo a norma de ensaios ASTM E1820-96. Os corpos-de-prova compactos C(T) apresentaram espessura B=15mm, largura W=2B e uma relação aproximada entre o tamanho de trinca (a) e a largura, a/W=0,6. O ensaio foi conduzido numa máquina universal de ensaios (MTS) servo-controlada e capacidade máxima de 250kN. Adicionalmente, foram conduzidos ensaios convencionais de tração (limite de escoamento – 550MPa, limite de resistência – 676MPa e alongamento total em 50mm – 27%), ensaios de impacto Charpy (energia absorvida de 220J à 0ºC – sentido longitudinal) e análises metalográficas (microestrutura refinada composta por ferrita, colônias de perlita e presença do constituinte MA). Tais caracterizações permitirão uma maior precisão na comparação da curva J-R do aço API 5L X80 em estudo com estudos futuros de tenacidade à fratura. / Assessments of crack growth resistance in ductile materials play a key role in structural integrity procedures for high strength, low alloy (HSLA) pipeline steels commonly employed in gas and petroleum trasmission systems. This work presents an investigation of the ductile tearing properties for an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-R curves) for the material. Testing of the X80 pipeline steel employed compact tension (C(T)) fracture specimens to determine the J-R curves based upon the unloading compliance method using a single specimen technique in accordance with the ASTM E1820 standard procedure. The C(T) specimens have thickness B=15mm, width W=2B and a ratio between crack size (a) and width, a/W=0,6. The experimental tests utilized a 250 kN MTS universal machine. Conventional tensile tests were also performed to determine the tensile properties for the tested material: yield strength of 550MPa, tensile strength of 676MPa and elongation of 27% (gage length of 50 mm). The Charpy V-notch impact tests also provided and absorbed energy of 220J at 0ºC. The metallographic analysis showed colonies of perlite and MA constituent islands in a ferrite matrix. This experimental characterization provides additional toughness and mechanical data against which the general behavior of X80 class pipeline steel can be compared.